Bacterial endospores derive much of their longevity and resistance properties from therelative dehydration of their protoplasts. This dehydration is maintained by a surrounding peptidoglycan structure, the spore cortex. A structural modification unique to,the spore cortex is removal of all or part of the peptide side chains from the majority of the muramic acid residues andconversion of 50% of the muramic acid to muramic lactam. A mutation in the cwLD gene of Bacillus subtilis, predicted to encode a muramoyl-L-alanine amidase, results in the production of spores containing no muramic lactam. These spores have normally dehydrated protoplasts but are unable to complete the germination/outgrowth process to produce viable cells. Our objective is a detailed understanding of formation and maintenance of a dormant, resistant bacterial (Bacillus subtilis) spore. The aims are: a) analyze the sequence, regulation and function of additional genes encoding penicillin-binding proteins (PBP); b) with strains lacking one or more PBPs, analyze the cortex structure and heat resistance of their spores; and c) identify the enzyme(s) initiating cortex hydrolysis during spore germination. Work being carried out with B. suhtilis should yield knowledge applicable to other Gram-positive spore formers. The latter organisms are significant agents of food spoilage and food-borne human disease, largely because of the resistant nature of spores. Thus knowledge gained herein could have significant applications. Muropeptide structures are determined by amino acid/amino sugar analysis and NLAJ-DI-TOF MS.